A. Field of the Invention
The present invention relates to manipulator apparatus and more particularly to manipulator apparatus which may be controlled by the sensing of the position of the manipulator arm and by the sensing of the dynamics of the end of the manipulator arm.
B. Description of the Prior Art
Various types of manipulator apparatus are controlled by the comparison of command signals which are stored in memory and readout in a replay mode with position signals developed by encoders representing the position of the manipulator arm in each of various controlled axes.
Such programmable manipulators are shown, for example, in Devol U.S. Pat. No. 3,306,471 dated Feb. 28, 1967; Devol U.S. Pat. No. 3,543,947 dated Dec. 1, 1970; Dunne, et al U.S. Pat. No. 3,661,051 dated May 9, 1972; Engelberger, et al U.S. Pat. No. 3,744,032 dated July 3, 1973; Engelberger, et al U.S. Pat. No. 3,885,295 dated May 27, 1975; Devol, et al U.S. Pat. No. 3,890,552 dated June 17, 1975; and British Pat. No. 781,465. While these arrangements have, in general, been satisfactory for their intended purpose, they are not entirely suitable for applications involving manipulator arms having combinations of high tip velocities, long arm extensions as measured from the center of the drive train of the apparatus, and appreciable arm and load masses.
In these applications as well as many related applications, the control of the arm is complicated by the fact that the position sensing occurs at a location which is remote from the actual end of the manipulator arm and the signal developed by the position encoder may not correspond to the actual position of the end of the manipulator arm. With these arrangements the dynamics of the arm greatly influence the actual position of the arm relative to the sensed and commanded position as a result of the indirect position sensing.
This results in instantaneous control problems such as the whipping of the arm, overshoot, increased settling time or perturbation effects. In addition to the control of manipulator apparatus, these problems also occur in other applications of indirect position sensing as in the control of an automatic crane moving large masses and having a long projecting arm and also where manipulator arms extend into furnaces. Further, complications in controlling manipulator apparatus and related apparatus occur when the various controlled axes are interconnected so that the dynamics of the various axes can not be measured separately for each axis.